Field of the Invention
The invention relates, in general, to a digital memory and to a method of operating a digital memory.
For dynamic memories (DRAMs), operating modes that can be stipulated by the memory manufacturer are based on a JEDEC standard. The JEDEC standard merely defines how to change from a normal operating mode to additional operating modes. Often, these additional operating modes are manufacturer-specific test operating modes. According to the JEDEC standard, a change into these additional operating modes can be performed by applying prescribed signal combinations to the standard external connections of the DRAM.
When a memory is operating, and particularly, when the memory is being tested, it is desirable to be able to establish whether an intentional change of operating modes has actually taken place, or whether an unintentional change has occurred by chance. However, the presented problem is that the number of external connections of a DRAM is limited, so that, under some circumstances, none of the connections can be used to output an appropriate status signal that can give information about the particular operating mode.